Which one of the following does not exist ?
`(i) XeOF_(4) (ii) NeF_(2) (iii) XeF_(2) (iv) XeF_(6)`.

Answer

To determine which of the given compounds does not exist, we will analyze each option based on the properties of the elements involved, particularly focusing on their electronic configurations and the ability to form compounds.

### Step-by-Step Solution:

1. **Identify the Compounds**:
The compounds given are:
- (i) XeOF₄
- (ii) NeF₂
- (iii) XeF₂
- (iv) XeF₆

2. **Analyze Each Compound**:
- **(i) XeOF₄**:
- Xenon (Xe) can form compounds with oxygen and fluorine due to its ability to expand its octet. Therefore, XeOF₄ exists.

- **(ii) NeF₂**:
- Neon (Ne) is a noble gas with a complete octet (1s² 2s² 2p⁶). It does not have vacant d-orbitals or the ability to expand its valence shell. Therefore, NeF₂ does not exist.

- **(iii) XeF₂**:
- Xenon can form XeF₂ as it has vacant d-orbitals and can accommodate more than 8 electrons. Thus, XeF₂ exists.

- **(iv) XeF₆**:
- Similarly, XeF₆ is known to exist as xenon can utilize its d-orbitals to form this compound.

3. **Conclusion**:
After analyzing all options, we find that the only compound that does not exist is **NeF₂**.

### Final Answer:
The compound that does not exist is **(ii) NeF₂**.

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